Wednesday, April 11, 2018

Access XAF Application Data in a non-XAF Application

In certain scenarios, you may need to create an axillary application for database maintenance and use Object Space to query your primary XAF application data. This topic describes how you can create and use Object Space in a regular non-XAF application.

Important

We do not recommend using the approach described here in XAF applications. Instead, always use the XafApplication.CreateObjectSpace method or access an existing Object Space.

In a non-XAF application, you have no XafApplication object to create an Object Space. But, an XafApplication does not create Object Spaces itself. Internally, it uses the Object Space Provider designed to create Object Spaces for the currently used ORM and those registered in its overridden XafApplication.CreateDefaultObjectSpaceProvider method. In a non-XAF application, you can instantiate the Object Space Provider manually. In XPO-based applications, use the DevExpress.ExpressApp.Xpo.XPObjectSpaceProvider constructor for this purpose. In Entity Framework applications, use the DevExpress.ExpressApp.EF.EFObjectSpaceProvider. Then, you can call the provider's CreateObjectSpace method to create an Object Space.

Entity Framework Example

You can use the following code to access data of the EFDemo application (typically installed to %PUBLIC%\Documents\DevExpress Demos 17.2\Components\eXpressApp Framework\EFDemoCodeFirst) and write the list of Departments to the standard output stream.

using DevExpress.ExpressApp.EF;
using DevExpress.ExpressApp;
using EFDemo.Module.Data;
// ... 
class Program {
    static void Main(string[] args) {
        EFObjectSpaceProvider osProvider = new EFObjectSpaceProvider(typeof(EFDemoDbContext),
            "integrated security=True;multipleactiveresultsets=True;data source=(localdb)\\v11.0;initial catalog=EFDemo_17.2");
        IObjectSpace objectSpace = osProvider.CreateObjectSpace();
        foreach (Department department in objectSpace.GetObjects()) {
           Console.WriteLine(department.Title + "\t" + department.Office);
        }
    }
}

XPO Example

In XPO-based applications, you should additionally initialize the Types Info Subsystem. The following example demonstrates how to access data of the MainDemo application (typically installed to %PUBLIC%\Documents\DevExpress Demos 17.2\Components\eXpressApp Framework\MainDemo) and write the list of Departments to the standard output stream:

using DevExpress.ExpressApp.Xpo;
using DevExpress.ExpressApp;
using MainDemo.Module.BusinessObjects;
// ... 
class Program {
    static void Main(string[] args) {
        XpoTypesInfoHelper.GetXpoTypeInfoSource();
        XafTypesInfo.Instance.RegisterEntity(typeof(Department));
        XPObjectSpaceProvider osProvider = new XPObjectSpaceProvider(
        @"integrated security=SSPI;pooling=false;data source=(localdb)\v11.0;initial catalog=MainDemo_17.2", null);
        IObjectSpace objectSpace = osProvider.CreateObjectSpace();
        foreach (Department department in objectSpace.GetObjects()) {
            Console.WriteLine(department.Title + "\t" + department.Office);
        }
    }
}

If you need to populate the database with initial data, use the DatabaseUpdater.Update method as follows:

using DevExpress.ExpressApp.Updating;
// ... 
DatabaseUpdater databaseUpdater = new DatabaseUpdater(
    osProvider, new ModuleBase[0], "", osProvider.ModuleInfoType);
databaseUpdater.Update();

Ways to Implement Business Logic

There are two common places for your business logic code - Controllers and business classes themselves. In Controllers, you can declare new and customize existing Actions and handle other Controllers' events. In business classes, you can put logic into property getters and setters, implement methods that are triggered automatically when the object is created, loaded, saved and deleted (see IXafEntityObject) and declare action methods. In these cases, Object Space is required when data the current business object exposes is insufficient for your business logic, and you need to query more data. You may also use Object Space in your database initialization code, in complex View Items, etc. This topic describes the API you can use to get Object Space in various contexts.

Get an Existing Object Space

Usually, you can use an existing Object Space instance accessible via the XAF API. The following table describes how you can get an Object Space from various contexts of your code:

Context	Ways to Access Object Space	Examples
Business Object	An Object Space reference is automatically assigned to the IObjectSpaceLink.ObjectSpace property when a business object supporting an IObjectSpaceLink is instantiated. You can implement this interface and access other business objects directly in the current object code using the Object Space passed to the ObjectSpace property. If you additionally implement an IXafEntityObject, then you can place your logic into the IXafEntityObject.OnCreated, IXafEntityObject.OnLoaded and IXafEntityObject.OnSaving methods. You can use the XAF Business Object \| EF Business Object from Template Gallery to add a class that supports both IXafEntityObject and IObjectSpaceLink. We recommend using Controllers instead of accessing UI-related entities (Views, Controllers, Actions) and executing UI-specific logic within the business class code, because it violates the separation of concerns principle and is against the MVC architecture.	IXafEntityObject
Controller	In XAF applications, an Object Space is automatically assigned for each View. In a View Controller, you can get the current View using the ViewController.View property. Then, access the Object Space with the View.ObjectSpace. You can also use the protected ViewController.ObjectSpace property that refers to the same Object Space as View.ObjectSpace. A Window Controller does not expose a View directly. You can access the current Frame using the Controller.Frame property and get the View with Frame.View. A View handles Object Space events to update the UI each time an object changes. We recommend creating a new Object Space that is not bound to a current View instead of using theView.ObjectSpace property to process large amounts of data. You should also use a new Object Space when you create a new View with the XafApplication.CreateListView or XafApplication.CreateDetailView methods.	Add a Simple Action using an Attribute Add an Action that Displays a Pop-up Window Add an Action with Option Selection IObjectSpace.ObjectChanged
Module Updater	In a ModuleUpdater descendant, you can use the protected ModuleUpdater.ObjectSpace property to access the Object Space instance that can be used for database update operations. Do not use a new Object Space to update the database.	Supply Initial Data (EF) Supply Initial Data (XPO)
List Editor	A reference to the CollectionSourceBase object is automatically passed to the IComplexListEditor.Setup method if your custom List Editor supports the IComplexListEditor interface. You can implement this interface and access the Object Space via the CollectionSourceBase.ObjectSpace property.
View Item or Property Editor	A reference to an Object Space is automatically passed to the IComplexViewItem.Setup method if your custom View Item or Property Editor supports the IComplexViewItem interface. You can implement this interface and store the Object Space reference to a local variable for future use.	IComplexViewItem

Object Space is also available using arguments passed to various events of the XafApplication class.

Event	Object Space Parameter
XafApplication.CreateCustomCollectionSource	CreateCustomCollectionSourceEventArgs.ObjectSpace
XafApplication.CreateCustomLogonWindowObjectSpace	CreateCustomPropertyCollectionSourceEventArgs.ObjectSpace
XafApplication.CreateCustomPropertyCollectionSource	CreateCustomLogonWindowObjectSpaceEventArgs.ObjectSpace
XafApplication.ObjectSpaceCreated	ObjectSpaceCreatedEventArgs.ObjectSpace
XafApplication.ViewCreating	ViewCreatingEventArgs.ObjectSpace

Create a New Object Space

It is often necessary to instantiate a new Object Space (for example, when you create a View using the XafApplication.CreateListView or XafApplication.CreateDetailView methods). Use the XafApplication.CreateObjectSpace method instead of an Object Space constructor to create an Object Space. For instance, the Controller.Application property is available in a Controller context, and you can create an Object Space as follows:

IObjectSpace objectSpace = this.Application.CreateObjectSpace();

Refer to the XafApplication class description to see how to obtain an XafApplication instance in various contexts. You cannot create new Object Spaces in the business object context because an XafApplication instance is not available there.

Examples:

Important

You should manually dispose of an Object Space when you are finished using it if you do not assign it to a View. An Object Space associated with a View is removed automatically together with this View.

Once you have obtained or created an Object Space, you can use it to query or modify data (see Create, Read, Update and Delete Data).

Create, Read, Update and Delete Data

Once you have obtained or created an Object Space instance (as described in the Ways to Implement Business Logic topic), you can use it to create, read, update or delete data. This topic lists common data-aware operations with the corresponding Object Space methods and events.

Data Manipulation	Related IObjectSpace Members
Create a new object	Methods: IObjectSpace.CreateObject IObjectSpace.CreateObject IObjectSpace.IsNewObject
Get a single object	Methods: IObjectSpace.FindObject IObjectSpace.FindObject IObjectSpace.GetObject IObjectSpace.GetObjectByKey IObjectSpace.GetObjectByKey IObjectSpace.GetObjectByHandle IObjectSpace.IsObjectFitForCriteria
Get a collection	Methods: IObjectSpace.GetObjects IObjectSpace.GetObjects IObjectSpace.CreateDataView IObjectSpace.CreateServerCollection IObjectSpace.CreateCollection IObjectSpace.SetTopReturnedObjectsCount IObjectSpace.GetObjectsQuery
Count objects	Methods: IObjectSpace.GetObjectsCount
Save	Methods: IObjectSpace.CommitChanges IObjectSpace.IsObjectToSave IObjectSpace.GetObjectsToSave Properties: IObjectSpace.IsCommitting Events: IObjectSpace.Committing IObjectSpace.Committed IObjectSpace.CustomCommitChanges IObjectSpace.ObjectSaving IObjectSpace.ObjectSaved
Delete	Methods: IObjectSpace.Delete IObjectSpace.IsObjectToDelete IObjectSpace.GetObjectsToDelete Properties: IObjectSpace.IsDeleting Events: IObjectSpace.ObjectDeleting IObjectSpace.ObjectDeleted
Track modifications	Methods: IObjectSpace.SetModified Properties: IObjectSpace.ModifiedObjects IObjectSpace.IsModified Events: IObjectSpace.ObjectChanged IObjectSpace.ModifiedChanged IObjectSpace.ModifiedChanged
Refresh and rollback	Methods: IObjectSpace.Refresh IObjectSpace.ReloadObject IObjectSpace.Rollback Events: IObjectSpace.Refreshing IObjectSpace.Reloaded IObjectSpace.ObjectReloaded IObjectSpace.CustomRefresh IObjectSpace.RollingBack IObjectSpace.CustomRollBack

For details, refer to the descriptions of these members.

Friday, April 6, 2018

XAF BO Template

Table Annotation

Default field

[XafDisplayName("备注")]

[MaxLength(255)]

public string Remark { get; set; }

[XafDisplayName("创立日期")]

public DateTime? CreatedOn { get; set; }

[XafDisplayName("创立人")]

public PermissionPolicyUser CreatedBy { get; set; }

[XafDisplayName("更新日期")]

public DateTime? UpdatedOn { get; set; }

[XafDisplayName("更新人")]

public PermissionPolicyUser UpdatedBy { get; set; }

Master-Detail (One to many)

Master

public IM_Request()
{
IM_RequestFiles = new List();
}

[DevExpress.ExpressApp.DC.Aggregated]
public virtual IList IM_RequestFiles { get; set; }

Detail

public virtual IM_Request IM_Request { get; set; }

Thursday, March 29, 2018

Programming Concepts (C#)

07/20/2015
2 minutes to read
Contributors

This section explains programming concepts in the C# language.

In This Section

Title	Description
Assemblies and the Global Assembly Cache (C#)	Describes how to create and use assemblies.
Asynchronous Programming with async and await (C#)	Describes how to write asynchronous solutions by using the async and awaitkeywords in C#. Includes a walkthrough.
Attributes (C#)	Discusses how to provide additional information about programming elements such as types, fields, methods, and properties by using attributes.
Caller Information (C#)	Describes how to obtain information about the caller of a method. This information includes the file path and the line number of the source code and the member name of the caller.
Collections (C#)	Describes some of the types of collections provided by the .NET Framework. Demonstrates how to use simple collections and collections of key/value pairs.
Covariance and Contravariance (C#)	Shows how to enable implicit conversion of generic type parameters in interfaces and delegates.
Expression Trees (C#)	Explains how you can use expression trees to enable dynamic modification of executable code.
Iterators (C#)	Describes iterators, which are used to step through collections and return elements one at a time.
Language-Integrated Query (LINQ) (C#)	Discusses the powerful query capabilities in the language syntax of C#, and the model for querying relational databases, XML documents, datasets, and in-memory collections.
Object-Oriented Programming (C#)	Describes common object-oriented concepts, including encapsulation, inheritance, and polymorphism.
Reflection (C#)	Explains how to use reflection to dynamically create an instance of a type, bind the type to an existing object, or get the type from an existing object and invoke its methods or access its fields and properties.
Serialization (C# )	Describes key concepts in binary, XML, and SOAP serialization.
Threading (C#)	Provides an overview of the .NET threading model and shows how to write code that performs multiple tasks at the same time to improve the performance and responsiveness of your applications.

LINQ - Query Operators

A set of extension methods forming a query pattern is known as LINQ Standard Query Operators. As building blocks of LINQ query expressions, these operators offer a range of query capabilities like filtering, sorting, projection, aggregation, etc.

LINQ standard query operators can be categorized into the following ones on the basis of their functionality.

Filtering Operators
Join Operators
Projection Operations
Sorting Operators
Grouping Operators
Conversions
Concatenation
Aggregation
Quantifier Operations
Partition Operations
Generation Operations
Set Operations
Equality
Element Operators

Filtering Operators

Filtering is an operation to restrict the result set such that it has only selected elements satisfying a particular condition.

Show Examples

Operator	Description	C# Query Expression Syntax	VB Query Expression Syntax
where	Filter values based on a predicate function	where	Where
OfType	Filter values based on their ability to be as a specified type	Not Applicable	Not Applicable

Join Operators

Joining refers to an operation in which data sources with difficult to follow relationships with each other in a direct way are targeted.

Show Examples

Operator	Description	C# Query Expression Syntax	VB Query Expression Syntax
Join	The operator join two sequences on basis of matching keys	join … in … on … equals …	From x In …, y In … Where x.a = y.a
GroupJoin	Join two sequences and group the matching elements	join … in … on … equals … into …	Group Join … In … On …

Projection Operations

Projection is an operation in which an object is transformed into an altogether new form with only specific properties.

Show Examples

Operator	Description	C# Query Expression Syntax	VB Query Expression Syntax
Select	The operator projects values on basis of a transform function	select	Select
SelectMany	The operator project the sequences of values which are based on a transform function as well as flattens them into a single sequence	Use multiple from clauses	Use multiple From clauses

Sorting Operators

A sorting operation allows ordering the elements of a sequence on basis of a single or more attributes.

Show Examples

Operator	Description	C# Query Expression Syntax	VB Query Expression Syntax
OrderBy	The operator sort values in an ascending order	orderby	Order By
OrderByDescending	The operator sort values in a descending order	orderby ... descending	Order By ... Descending
ThenBy	Executes a secondary sorting in an ascending order	orderby …, …	Order By …, …
ThenByDescending	Executes a secondary sorting in a descending order	orderby …, … descending	Order By …, … Descending
Reverse	Performs a reversal of the order of the elements in a collection	Not Applicable	Not Applicable

Grouping Operators

The operators put data into some groups based on a common shared attribute.

Show Examples

Operator	Description	C# Query Expression Syntax	VB Query Expression Syntax
GroupBy	Organize a sequence of items in groups and return them as an IEnumerable collection of type IGrouping	group … by -or- group … by … into …	Group … By … Into …
ToLookup	Execute a grouping operation in which a sequence of key pairs are returned	Not Applicable	Not Applicable

Conversions

The operators change the type of input objects and are used in a diverse range of applications.

Show Examples

Operator	Description	C# Query Expression Syntax	VB Query Expression Syntax
AsEnumerable	Returns the input typed as IEnumerable	Not Applicable	Not Applicable
AsQueryable	A (generic) IEnumerable is converted to a (generic) IQueryable	Not Applicable	Not Applicable
Cast	Performs casting of elements of a collection to a specified type	Use an explicitly typed range variable. Eg:from string str in words	From … As …
OfType	Filters values on basis of their , depending on their capability to be cast to a particular type	Not Applicable	Not Applicable
ToArray	Forces query execution and does conversion of a collection to an array	Not Applicable	Not Applicable
ToDictionary	On basis of a key selector function set elements into a Dictionary and forces execution of a LINQ query	Not Applicable	Not Applicable
ToList	Forces execution of a query by converting a collection to a List	Not Applicable	Not Applicable
ToLookup	Forces execution of a query and put elements into a Lookup on basis of a key selector function	Not Applicable	Not Applicable

Concatenation

Performs concatenation of two sequences and is quite similar to the Union operator in terms of its operation except of the fact that this does not remove duplicates.

Show Examples

Operator	Description	C# Query Expression Syntax	VB Query Expression Syntax
Concat	Two sequences are concatenated for the formation of a single one sequence.	Not Applicable	Not Applicable

Aggregation

Performs any type of desired aggregation and allows creating custom aggregations in LINQ.

Show Examples

Operator	Description	C# Query Expression Syntax	VB Query Expression Syntax
Aggregate	Operates on the values of a collection to perform custom aggregation operation	Not Applicable	Not Applicable
Average	Average value of a collection of values is calculated	Not Applicable	Aggregate … In … Into Average()
Count	Counts the elements satisfying a predicate function within collection	Not Applicable	Aggregate … In … Into Count()
LonCount	Counts the elements satisfying a predicate function within a huge collection	Not Applicable	Aggregate … In … Into LongCount()
Max	Find out the maximum value within a collection	Not Applicable	Aggregate … In … Into Max()
Min	Find out the minimum value existing within a collection	Not Applicable	Aggregate … In … Into Min()
Sum	Find out the sum of a values within a collection	Not Applicable	Aggregate … In … Into Sum()

Quantifier Operations

These operators return a Boolean value i.e. True or False when some or all elements within a sequence satisfy a specific condition.

Show Examples

Operator	Description	C# Query Expression Syntax	VB Query Expression Syntax
All	Returns a value ‘True’ if all elements of a sequence satisfy a predicate condition	Not Applicable	Aggregate … In … Into All(…)
Any	Determines by searching a sequence that whether any element of the same satisfy a specified condition	Not Applicable	Aggregate … In … Into Any()
Contains	Returns a ‘True’ value if finds that a specific element is there in a sequence if the sequence doe not contains that specific element , ‘false’ value is returned	Not Applicable	Not Applicable

Partition Operators

Divide an input sequence into two separate sections without rearranging the elements of the sequence and then returning one of them.

Show Examples

Operator	Description	C# Query Expression Syntax	VB Query Expression Syntax
Skip	Skips some specified number of elements within a sequence and returns the remaining ones	Not Applicable	Skip
SkipWhile	Same as that of Skip with the only exception that number of elements to skip are specified by a Boolean condition	Not Applicable	Skip While
Take	Take a specified number of elements from a sequence and skip the remaining ones	Not Applicable	Take
TakeWhile	Same as that of Take except the fact that number of elements to take are specified by a Boolean condition	Not Applicable	Take While

Generation Operations

A new sequence of values is created by generational operators.

Show Examples

Operator	Description	C# Query Expression Syntax	VB Query Expression Syntax
DefaultIfEmpty	When applied to an empty sequence, generate a default element within a sequence	Not Applicable	Not Applicable
Empty	Returns an empty sequence of values and is the most simplest generational operator	Not Applicable	Not Applicable
Range	Generates a collection having a sequence of integers or numbers	Not Applicable	Not Applicable
Repeat	Generates a sequence containing repeated values of a specific length	Not Applicable	Not Applicable

Set Operations

There are four operators for the set operations, each yielding a result based on different criteria.

Show Examples

Operator	Description	C# Query Expression Syntax	VB Query Expression Syntax
Distinct	Results a list of unique values from a collection by filtering duplicate data if any	Not Applicable	Distinct
Except	Compares the values of two collections and return the ones from one collection who are not in the other collection	Not Applicable	Not Applicable
Intersect	Returns the set of values found t be identical in two separate collections	Not Applicable	Not Applicable
Union	Combines content of two different collections into a single list that too without any duplicate content	Not Applicable	Not Applicable

Equality

Compares two sentences (enumerable ) and determine are they an exact match or not.

Show Examples

Operator	Description	C# Query Expression Syntax	VB Query Expression Syntax
SequenceEqual	Results a Boolean value if two sequences are found to be identical to each other	Not Applicable	Not Applicable

Element Operators

Except the DefaultIfEmpty, all the rest eight standard query element operators return a single element from a collection.

Show Examples

Operator	Description	C# Query Expression Syntax	VB Query Expression Syntax
ElementAt	Returns an element present within a specific index in a collection	Not Applicable	Not Applicable
ElementAtOrDefault	Same as ElementAt except of the fact that it also returns a default value in case the specific index is out of range	Not Applicable	Not Applicable
First	Retrieves the first element within a collection or the first element satisfying a specific condition	Not Applicable	Not Applicable
FirstOrDefault	Same as First except the fact that it also returns a default value in case there is no existence of such elements	Not Applicable	Not Applicable
Last	Retrieves the last element present in a collection or the last element satisfying a specific condition	Not Applicable	Not Applicable
LastOrDefault	Same as Last except the fact that it also returns a default value in case there is no existence of any such element	Not Applicable	Not Applicable
Single	Returns the lone element of a collection or the lone element that satisfy a certain condition	Not Applicable	Not Applicable
SingleOrDefault	Same as Single except that it also returns a default value if there is no existence of any such lone element	Not Applicable	Not Applicable
DefaultIfEmpty	Returns a default value if the collection or list is empty or null	Not Applicable	Not Applicable

Wednesday, April 11, 2018

Access XAF Application Data in a non-XAF Application

Access XAF Application Data in a non-XAF Application

Entity Framework Example

XPO Example

See Also

XAF implement Business Logic using ObjectSpace

Ways to Implement Business Logic

Get an Existing Object Space

Create a New Object Space

See Also

ObjectSpace CRUD

Create, Read, Update and Delete Data

See Also

Friday, April 6, 2018

XAF BO Template

Table Annotation

Default field

Master-Detail (One to many)

Master

Detail

Thursday, March 29, 2018

Programming Concepts (C#)

Programming Concepts (C#)

In This Section

LINQ - Query Operators

Filtering Operators

Join Operators

Projection Operations

Sorting Operators

Grouping Operators

Conversions

Concatenation

Aggregation

Quantifier Operations

Partition Operators

Generation Operations

Set Operations

Equality

Element Operators